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Discussion Starter #1
my sled has had the carbs off 3 times this week and have been cleaned thoroughly, i am sure the floats are working right, but when i disconected the fuel line to the carb on the right side, fuel was still running through the line. even though the sled hasnt ran in a week. with the carbs off and plugs out, i pulled it for 10-15 minutes to get the large amount of fuel out....

does this sound like a simple primer problem? when i rode it yesterday, then let it idle for 2-3 minutes, it was flooding out as it was running, it almost stalled on me.

it runs great in open areas....but when in tight trails or at idle, it is very sluggish...

any help would be appreciated......

1993 ski-doo mach 1 670 rotax, has aftermarket pipe and can.
 

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OK, lets start with the basics, Check both your fuel pump's pulse lines for raw fuel in them. The 1993 low volume rubber diaphramed dual fuel pumps were prone to piercing after one good backfire. They also deteriorate faster than the newer fibre diaphrams. If there is fuel in the pulse lines, that's where the additional fuel is getting in. Now that we've eliminated that, check your primer with the engine running, is fuel being pulled through the primer lines?, another source for additional fuel. That's eliminated too ?, let's look at the VM40 carbs. The PTO and MAG differ in jetting, PTO 420 and MAG 440 for -20 C (0 F). Pilot jets 40, Jet Needle clip position from the top are PTO #1 and MAG #2, Air Screw 1/2 turn out from lightly seated. Float level 17 mm - 19 mm measured from the gasket flange. Lastly, idle speed 1800 - 2000 RPM warm engine. Get all these items done and there's no reason for carb related problems. Do you want to continue with secondary ignition problems?.
 

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Discussion Starter #3
OK, lets start with the basics, Check both your fuel pump's pulse lines for raw fuel in them. The 1993 low volume rubber diaphramed dual fuel pumps were prone to piercing after one good backfire. They also deteriorate faster than the newer fibre diaphrams. If there is fuel in the pulse lines, that's where the additional fuel is getting in. Now that we've eliminated that, check your primer with the engine running, is fuel being pulled through the primer lines?, another source for additional fuel. That's eliminated too ?, let's look at the VM40 carbs. The PTO and MAG differ in jetting, PTO 420 and MAG 440 for -20 C (0 F). Pilot jets 40, Jet Needle clip position from the top are PTO #1 and MAG #2, Air Screw 1/2 turn out from lightly seated. Float level 17 mm - 19 mm measured from the gasket flange. Lastly, idle speed 1800 - 2000 RPM warm engine. Get all these items done and there's no reason for carb related problems. Do you want to continue with secondary ignition problems?.[/b]


I am not that knowledged with the names of the lines yet, but if the pulse line is the larger of the two lines connected to a carb......there is definitely a constant drip from the line without the machine running non pto side. (carbs are labelled).....i had to turn the gas off at the valves......so if that is the line you are talking about i think i know what the source of the problem is...... just not sure how to fix it.......

once again...thanks for the advice ThumbDoc........
 

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I am not that knowledged with the names of the lines yet, but if the pulse line is the larger of the two lines connected to a carb......there is definitely a constant drip from the line without the machine running non pto side. (carbs are labelled).....i had to turn the gas off at the valves......so if that is the line you are talking about i think i know what the source of the problem is...... just not sure how to fix it.......

once again...thanks for the advice ThumbDoc........[/b]
No the pulse lines are those which go from the two fuel pumps to the engine crankcase. The crankcase compression / vacuum sends a pulse to the back side of a diaphram in the pump housing which on it's other side pulls fresh gas from the gas tank through a series of one way valves up to the carburetors.
 

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Discussion Starter #5
No the pulse lines are those which go from the two fuel pumps to the engine crankcase. The crankcase compression / vacuum sends a pulse to the back side of a diaphram in the pump housing which on it's other side pulls fresh gas from the gas tank through a series of one way valves up to the carburetors.[/b]
so are the fuel pumps rebuildable? or should the whole pumps be replaced? i'm under the impression that the sled has been sitting for 3-4 seasons so am thinking tthat further problems could arise if i dont take care of them now...... I was told to expect about 40-50 dollars per pump, does that sound right?


i have the pumps accessable , carbs out, labelled, and bagged. fuel was still coming out of the line once i turned on the fuel switch, so i think i may have found the problem.......
 

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so are the fuel pumps rebuildable? or should the whole pumps be replaced? i'm under the impression that the sled has been sitting for 3-4 seasons so am thinking tthat further problems could arise if i dont take care of them now...... I was told to expect about 40-50 dollars per pump, does that sound right?
i have the pumps accessable , carbs out, labelled, and bagged. fuel was still coming out of the line once i turned on the fuel switch, so i think i may have found the problem.......[/b]
Those particular pumps are rebuildable for about 12 dollar per kit. I would at least disassemble one of them to evaluate whether rebuilding or replacing is the better option. Keep in mind, if it's rebuild it can be a DIY seeing that it would not be any savings paying someone else to do it. The support is always here.
 

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Discussion Starter #7
Those particular pumps are rebuildable for about 12 dollar per kit. I would at least disassemble one of them to evaluate whether rebuilding or replacing is the better option. Keep in mind, if it's rebuild it can be a DIY seeing that it would not be any savings paying someone else to do it. The support is always here.[/b]

thanks once again ThumbDoc....... i'll start making calls in the morning.....
 

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Thanks ThumbDoc..... I installed a new fuel pump and it appears to be running smoother. I am going to rebuild the pump i removed and plan on installing it in place of the othe one left. Unfortunately i paid allot more for the pump, but i was supporting local business so i guess it works out......i'll know better tomorrow if it worked for sure, once it has sat over night.
 

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my sled sounds like i may have the same problem. i got the sled it sat for 3 years cleaned everything out. i was riding it for a while it always seemed to idle to high about 3500 sometimes 4000, never really cared cause it never stalled or anything. this morning i went out had a hell of a time pulling it over i had to use some quick start, it barly helped. i parked it infront of the garage decided id better turn down the idle. well now i cant get it going my shoulder hurts and i got the felling this isnt going to be cheap. i read the intire page kinda sounds like i have the same problem any advice is apreciated, i dont no much about sleds but if you put it simple ill probly understand.
 

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My dad just bought a new snowmobile and his seems to be having that same problem. It is a 1999 Arctic Cat 700 powder Special and the guy we bought it from started it up and rode it for a short while and parked it and then went to get back on it and it wouldnt start. He pulled the spark plugs and pulled the rope and fuel sprayed from both carbs. Not dealing with snowmobiles much at all, does this sound like the fuel pump problem as mentioned above or possibly something electronic? it does have an electrical plug on one of the carbs? any response would be GREATLY appreciated. Thanks
 
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